I'm interested in shipping wine from Italy into the US. I have some family on vacation in Italy right now and they would like to send some of the wine they've already purchased to the US, California specifically. What are the legalities of doing this? If it is legal, how much does something like this cost per case and who would you use to do the shipping?

The easiest way is for them to bring it back with them; either in their luggage or in shipping containers usually available at wineries or sometimes at retailers. All the wine should be declared on the customs declaration, and at worst a very small charge will be made. Usually the paperwork is not worth it and they will just be waved through. If they don't declare it, there will be hell to pay.